Two enzymes involved in the early stages of pantothenate biosynthesis, specifically alpha-ketopantoate hydroxymethyltransferase and pantoate dehydrogenase, are being further studied with respect to molecular weight, subunit structure, substrate specificity, and control properties. An unrelated enzyme, histidine decarboxylase from Lactobacillus 30a which contains a pyruvoyl prosthetic group, is also being studied with respect to its mechanism of action and expecially the mechanism of its formation from a purified proenzyme which contains no bound pyruvate. In addition, we are studying the comparative uptake of labeled pantothenate by Salmonella typhimurium and other organisms, together with the nature of the uptake system and the kinetics of transformation of this vitamin to its derived forms. We will also initiate a study of the metabolic disposition of excess pantothenate in animals (rats). These projects are carried out in close connection with those supported by a second USPHS grant entitled "Catalytic Functions and Metabolism of Vitamin B6", AM 01448.